A flap as a high-lift device is provided at a trailing-edge of a main wing of an aircraft. The flap is deployed rearward and downward during take-off and landing, and thus necessary lift is generated.
With the flap being deployed from the main wing, a tip vortex is generated at the flap tip. The tip vortex flows on the upper surface of the flap, and noise is generated from pressure fluctuations resulting from that vortex on the surface of the flap. Although not limited to the flap provided to the aircraft, a wing as an object having a shape capable of efficiently obtaining lift by interactions with a fluid generates noise resulting from the wing tip vortex as described above.
Patent Document 1 discloses a technology of providing, in order to reduce such noise, a flow suppression portion on the upper surface side of a leading-edge of a tip end of a flap main body, the flow suppression portion separating a flow along the upper surface of the tip end.
In other words, the technology disclosed in Patent Document 1 separates the flow along the upper surface of the tip end of the flap main body and reduces lift at a flap end, to thus weaken a vortex at the flap end and reduce noise.